Looking Up: Night sky is full of tails

Guess what. A few years ago, NASA found that our solar system has a tail.

No, we haven’t heard that it is wagging and a far as we know the only one that has caught it is NASA’s Interstellar Boundary Explorer space probe. This was in 2009.

This tail is a stream of charged particles originating in the Sun. They stream backwards from the Sun’s path of travel through galactic space. The effect is a long tail pointing back from where the Sun (and its planets) has come.

The spacecraft, launched in 2008, is mapping the turbulent boundary far beyond Pluto, between interstellar space and the the heliosphere. An article in Sky and Telescope explained that charged particles and magnetic field lines flowing from the Sun as the “solar wind” make up an enormous bubble encasing the solar system, called the heliosphere. Interaction between these particles and the hydrogen atoms in deep space are detected by the craft.

The mapping revealed the tail looking “downwind” in the direction of where the constellations Orion and Taurus meet on the winter evening sky. The Sun, along with the Earth and other planets is heading roughly towards the bright star Vega in the constellation Hercules, well seen in the summer evening sky.

Hurtling forward with its great tail, the solar system is moving at approximately 136.7 miles a second. At this rate we travel an entire light year in 1,400 years. Note, the distance to the nearest other star system, Alpha Centauri, is 4.3 light years. The Milky Way Galaxy is big indeed. It takes the Sun as much as 240 million years to orbit once around the galaxy, with all the other stars moving as well.

The tail isn’t something you would easily see “from out there”- no more than you could see the wind blowing. A tail of charged particles, however, has been photographed streaming back from another star, a famous variable star named Mira. It was pictured in ultraviolet light by NASA’s Galaxy Evolution Explorer space telescope. Mira’s tail is 13 light years long.

The tail looks a lot like a comet tail. The solar wind is also responsible for pushing back the fine dust and gas from a melting comet as it passes by the Sun, creating a long vaporous tail.

NASA reports that nearly a dozen competing theories have been introduced to explain this phenomenon.

Tails of course are well known to backyard astronomers. I’ve had plenty of cats come by in the dark while I’m trying to look through the telescope.

The constellations also sport quite a few tails- depending on how you connect the stars. Those with tails include Leo the Lion, Draco the Dragon, Canis Major the Big Dog, Hydra the Sea Serpent, Cygnus the Swan and even Ursa Major the Big Bear. Ever see a bear with a long tail? The Big Dipper is part of the Bear constellation, and some see the Dipper’s “handle” as the tail!

Enough of this “tail.”

For more information on the IBEX space mission, visit: http://www.nasa.gov/ibex .

Full Moon is on Sept. 6.

Keep looking up!

— Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.

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